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United States Patent |
5,642,172
|
Yoon
,   et al.
|
June 24, 1997
|
Image processing system for adjusting the image characteristics of a
display system
Abstract
An image compensation system and methods for video appliances to reproduce
an optimum image, by the judged exterior environment and by compensating
for an original image by judging exterior environment. According to the
system and methods, a color sensor senses color of exterior lighting of an
appliance, and provides electrical signals corresponding to color
components of the sensed color. The signals are converted into a digital
value by an analog-to-digital converter. A microprocessor judges the type
of exterior lighting, by the digitized values, and searches for image
compensation data according to the judged exterior lighting. It thereby
makes a video processor compensate for an original image signal.
Inventors:
|
Yoon; Sang Han (Taegu, KR);
Ha; Yeoung Ho (Taegu, KR)
|
Assignee:
|
LG Electronics Inc. (Youngdungpo-gu, KR)
|
Appl. No.:
|
398497 |
Filed:
|
March 9, 1995 |
Foreign Application Priority Data
Current U.S. Class: |
348/603; 348/227.1 |
Intern'l Class: |
H04N 009/16; H04N 009/64 |
Field of Search: |
348/227,602,603
|
References Cited
U.S. Patent Documents
4584598 | Apr., 1986 | Kutaragi | 348/227.
|
4827332 | May., 1989 | Miyake et al. | 348/227.
|
5132825 | Jul., 1992 | Miyadera | 348/227.
|
5504525 | Apr., 1996 | Suzcki | 348/229.
|
Primary Examiner: Peng; John K.
Assistant Examiner: Flynn; Nathan J.
Attorney, Agent or Firm: Christie, Parker & Hale, LLP
Claims
What is claimed is:
1. An image compensation method for video appliances, comprising the steps
of:
sensing ambient light and providing a plurality of electrical signals each
respectively corresponding to one of a plurality of color components of
said ambient light;
summing values representing two or more of said plurality of electrical
signals corresponding to said respective color components;
determining an ambient light mode based on said summed value;
producing a set of image compensation data corresponding to said determined
ambient light mode; and
compensating an original image signal utilizing said set of image
compensation data.
2. An image compensation method for video appliances, comprising the steps
of:
sensing ambient light and providing a plurality of electrical signals each
respectively corresponding to one of a plurality of color components of
said ambient light;
summing values representing two or more of said plurality of electrical
signals corresponding to said respective color components;
determining an ambient light mode based on said summed value;
producing a first set of image compensation data corresponding to said
determined ambient light mode;
producing a second set of image compensation data based on said summed
value and correlation between said two or more values; and
compensating an original image signal utilizing said first and second sets
of image compensation data.
3. An image compensation system for a video appliance, comprising:
a sensor for generating a plurality of color signals, each color signal
corresponding respectively to one of a plurality of color components of
ambient light incident on said sensor;
a memory for storing a plurality of sets of compensation data, each set
corresponding respectively to one of a plurality of ambient light modes
and representing a plurality of image display characteristics; and
a microcontroller comprising means for determining the respective ambient
light mode based on a summation of two or more of said plurality of color
signals, and means for selecting the set of compensation date stored in
memory corresponding to the determined respective ambient light mode, said
microcontroller generating a compensation signal based on the set of
compensation data selected by the selecting means.
4. The image compensation system of claim 3, wherein the determining means
determines the respective ambient light mode based further on a
correlation of two or more of said plurality of color signals.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image compensation system and methods
for video appliances, such as a color television receiver, etc., which
compensates automatically for hue, saturation, contrast, brightness, and
white balance of an image, corresponding with the exterior environment of
the appliance.
2. Description of the Prior Art
Conventional video appliances, especially a television receiver generally
adopts a skin color compensation circuit and an automatic brightness
control circuit, as an image signal processor.
The skin color compensation circuit analyzes a received image signal, and
if the signal is judged as a human skin color, the circuit provides a
prescribed color, i.e., a skin color.
In practice, users often control human skin color when adjusting the
picture of a television receiver. Skin color plays a standard part in
adjusting the color of the picture.
The skin color compensation circuit, however, cannot properly cope with the
variety of skin colors, because it merely checks without regard to
exterior lightings whether or not an image signal is a skin color.
And it works in the same manner on colors analogous to skin color.
Therefore, an error in color reproduction may arise, and accordingly there
will be some limiting factors on natural color reproduction.
The automatic brightness control circuit controls the brightness of a
picture by sensing exterior brightness.
The attached FIG. 1 shows a bock diagram of a television receiver adopting
the automatic brightness control circuit.
The television receiver is, with reference to FIG. 1, composed of a tuner 1
for tuning to an aiming station in broadcasting signals received by an
antenna; an intermediate-frequency (hereinafter an "IF") signal processor
2 for processing an IF signal transformed from the tuned signal; a
detector 3 for detecting an image signal and an audio signal from the IF
signal processor 2; an audio processor 4 for processing the audio signal
detected from the detector 3; a speaker 5 for making audio sound from the
processed audio signal; a key selector 6, such as a key matrix, a remote
control or the like, for providing a user's key instruction; a
microprocessor unit (hereinafter an "MPU") 7 for allowing the tuner 1 to
select an aiming station according to a user's key instruction, and for
adjusting brightness of a picture by controlling the following video
processor 8, corresponding with exterior brightness detected by the
following brightness detector 10; a video processor 8 for controlling the
brightness of a picture under the control of the MPU 7; a picture tube 9
for displaying the image processed by the video processor 8; and a
brightness detector 10 for detecting exterior brightness, which provides
it to the MPU 7.
In operation, the MPU 7 controls the tuner 1 to select an aiming station
according to the instruction from the key selector 6. The selected station
signal is transformed into an IF signal at the IF signal processor 2. The
IF signal is provided to the detector 3.
The detector 3 detects an image signal and an audio signal from the IF
signal and provides the image signal to the video processor 8 and the
audio signal to the audio processor 4.
The audio processor 4 performs amplification of the audio signal and
various functions, such as stereo reproduction or multivoice processing,
and provides the processed signal to the speaker 5.
The video processor 8 performs amplification of the image signal and
processing a color signal and a luminance signal, and provides the
processed signals to the picture tube 9.
The brightness detector 10 detects exterior brightness using a sensor, such
as a photoconductive cell (CdS), and converts the detected signal into a
digital signal by an analog-to-digital converter built in the brightness
detector 10.
The digitized signal is provided to the MPU 7. The MPU 7 performs an
appropriate operation by using original brightness data CD, exterior
brightness data Cl, and reference data CO, e.g., CD=CD.times.Cl/CO, and
provides the resulting value to the video processor 8.
The video processor 8 compensates for the brightness data CD in accordance
with the exterior brightness data Cl, and thereby the brightness of the
picture tube 9 can be adjusted.
In such an automatic brightness control circuit, however, it is difficult
to perform sufficient natural color reproduction because the circuit
processes brightness (or contrast) only.
In fact, it is necessary to control all the image reproduction factors,
i.e., hue, saturation, contrast, brightness, and white balance, for
complete natural color reproduction. Without collective control of these
factors, it is difficult to accomplish natural color reproduction, and it
is difficult to properly represent an image bearing natural colors.
SUMMARY OF THE INVENTION
The present invention, which is directed to avoiding such a problem,
reproduces an optimum image and performs complete natural color
reproduction, by judging the exterior environment by sensing exterior
lighting, and compensating for an original image based on the judged
exterior environment.
According to one feature of this invention, there is provided an image
compensation system for video appliances, comprising:
means for sensing a color of exterior lighting and for providing electrical
signals corresponding to color components of said sensed color;
an analog-to-digital converter for converting the output signals of said
color sensing means into a digital value;
means for processing the output signal of said analog-to-digital converter
under the instruction of a prepared program, having (i) a memory for
memorizing image compensation data corresponding to the color of exterior
lighting, (ii) means for searching for corresponding data among said image
compensation data, reading the output of said analog-to-digital converter,
and (iii) means for outputting the searched data; and
means for compensating for an original image signal utilizing the output
signal of said processing means.
According to another feature of this invention, there are provided image
compensation methods for video appliances, comprising the steps of:
sensing a color of exterior lighting and providing electrical signals
corresponding to color components of said sensed color;
digitizing said electrical signals corresponding to said color components;
judging exterior environment from said digitized signal;
searching for image compensation data corresponding to said exterior
environment; and
compensating for an original image signal utilizing said image compensation
data.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features, aspects, and advantages of the present invention
will become better understood with regard to the following description,
appended claims, and accompanying drawings where:
FIG. 1 is a block diagram of a television receiver adopting a conventional
automatic brightness control circuit;
FIG. 2 is a block diagram of a television receiver adopting an image
compensation system of the present invention;
FIG. 3 is a detailed block diagram of a color sensor/processor as depicted
in FIG. 2;
FIG. 4 is a flowchart explaining the general operations of the present
invention:
FIG. 5 is a table showing the output value of color components from a color
sensor, according to an exterior environment;
FIG. 6 is a view showing conditions of an exterior environment for storing
data;
FIGS. 7A and 7B are tables showing image compensation data according to the
summation of color components; and
FIGS 8A and 8B are flowcharts explaining the operation of another
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The operation of the present invention will be discussed in regard to FIG.
2 through FIG. 7.
Referring to FIG. 2, the system according to the present invention, an
image compensation system for video appliances, is composed of: a tuner
100 for tuning to an aiming station in broadcasting signals received by an
antenna; an IF signal processor 200 for processing an IF signal
transformed from the tuned signal; a detector 300 for detecting an image
signal and an audio signal from the IF signal processor 200; an audio
processor 400 for processing the audio signal detected form the detector
300; a speaker 500 for making audio sound from the processed audio signal;
a key selector 600, such as a key matrix, a remote control or the like,
for providing a user'key instruction; an MPU 700 for allowing the tuner
100 to select an aiming station in accordance with a user'key instruction,
and for adjusting brightness of a picture by controlling the following
video processor 800, corresponding with exterior lightings and colors
detected by the following color sensor/processor 1000; a video processor
800 for compensating for an original image signal under the control of the
MPU 700; a picture tube 900 for displaying the image signal processed by
the video processor 800; and a color sensor/processor 1000 for sensing and
processing the exterior lightings and colors.
The color sensor/processor 1000 includes, referring to FIG. 3, a color
sensor 11A for decomposing incident light into the three primary colors,
i.e., red, green, and blue; an amplifier 11B for amplifying the color
signals from the color sensor 11A; a low-pass filter 11C for eliminating
noise from the amplified color signal; an analog-to-digital converter 11D
for converting the analog color signal from the low-pass filter 11C into a
digital signal.
The analog-to-digital converter is represented as an `ADC` in the drawings
for briefness. It may be equipped in the MPU 700 accordingly as the
function of a microcomputer or microprocessor has recently been expanded.
The operation of such a constructed system, an image compensation system
for video appliances, will be described with reference to FIGS. 2 and 3
and a flowchart in FIG. 4.
The MPU 700 controls the tuner 100 to select an aiming station in
broadcasting signals according to the instruction from the key selector
600. The selected station signal is transformed into an IF signal at the
IF signal processor 200, and is provided to the detector 300.
The detector 300 detects an image signal and an audio signal from the IF
signal, and provides the audio signal to the audio processor 400 and the
image signal to the video processor 800.
The audio processor 400 performs amplification of the audio signal and
various functions, such as stereo reproduction or multivoice processing,
and provides the processed signal to the speaker 500.
The video processor 800 performs amplification of the image signal and
processing a color signal and a luminance signal, and provides the
processed signals to the picture tube 900.
The color sensor/processor 1000 senses the color of exterior lightings,
such as sunlight or any other artificial light, and amplifies the color
signal and rejects noise. Thereafter the color sensor/processor 1000
provides the processed signal to the analog-to-digital converter 11D as
color data.
The MPU 700 finds the current exterior lighting environment using the
digitized color data. It thereafter provides a properly compensated image
data (hue, saturation, contrast, brightness, and white balance) to the
video processor 800.
Specifically, with reference to FIG. 3, the color sensor 11A decomposes the
exterior lighting, such as sunlight or any other artificial light, into
red (R), green (G), and blue (B). Because the output level of the color
sensor is weak, it is provided to the low-pass filter 11C after being
amplified by the amplifier 11B.
The low-pass filter 11C produces a purified color signal by eliminating
noise from the signal outputted from the amplifier 11B (in the case of
light bearing a low-frequency flicker, there is noise similar to a
sinusoidal wave).
The color signal passing through the low-pass filter 11C is converted into
a digital signal at the analog-to-digital converter 11D, and is provided
as color data to the MPU 700.
The color data being provided, the MPU 700 analyzes current exterior
lightings, and provides proper color compensation data to the video
processor 800 using the result of analysis.
In general, colors of R, G, and B are called the three primary colors of
light. By changing the mix ratio of the colors, almost all of the colors
can be represented on a picture tube. For instance, in the case of white
color, the projection degree of R, G, and B is `1`, respectively: in the
case of grey color, the projection degree is `0.5`, respectively. If the
three colors are not projected, black color is represented.
In contrast, a color sensor decomposes incident light into R, G, and B, and
provides electrical signals proportional to the amount of the color
components.
FIG. 5 shows an exemplary relative data of the output value of R, G, and B
where exterior environment is a fluorescent lamp, an incandescent lamp,
sunlight, or no light (darkroom).
The above data are served as reference data for judgement of what the
current exterior environment is, which are stored in a memory in a
microprocessor.
The general operation of the present invention will be described with
reference to a flowchart in FIG. 4.
The MPU 700 reads a quantized color data (digitized output of the color
sensor) directing the current exterior lightings, and judges thereby the
exterior environment mode. It finds thereafter an original image mode to
be outputted by retrieving the color data entering the video processor
800, and compares the original image mode with the exterior environment
mode.
Here, although image compensation can be performed for all of the quantized
color data from the color sensor, a processing sequence may become too
complicated. In addition, because human eyesight is, as a matter of fact,
not able to distinguish delicate color differences, only the artificial
light used for common homes and natural light (including weather
conditions and times) were taken into consideration.
That is, as shown in FIG. 6, taking a fine day, a cloudy day, a rainy day,
a morning, a noon, an evening, a night, a fluorescent lamp, an
incandescent lamp, and no light (a darkroom) as factors for judgement to
exterior environment, 36 kinds of exterior environment modes can be set.
Since the correlation between night and weather is low and if the case
that similar outputs are provided is considered, the number of cases may
be reduced to an appropriate extent.
The exterior environment mode may be determined not only when the color
data from the color sensor 11A is completely in accord with the prescribed
reference data but also when the color data lies within the prescribed
range.
In such cases, the MPU 700 compares the original image mode to be outputted
with the exterior environment mode now being inputted.
If the two modes are the same, the MPU 700 outputs the untreated original
image data to the video processor 800, and maintains the original image
mode.
If the two modes are different, the MPU 700 compensates for the original
image data by the determined exterior environment mode, and provides the
compensated image mode to the video processor 800. Accordingly, the
compensated image bearing the optimum hue, saturation, brightness,
contrast, and white balance, which are in accordance with the exterior
environment, is displayed on the picture tube 900.
Taking a set whose brightness step, saturation step, and contrast step
respectively range from 0 to 62 and hue step ranges from -31 to +31 as an
actual example, the set provides an image of hue=0, saturation=31,
brightness=31, contrast=62, and white balance=9000K in the caes of no
light (a darkroom); the set provides an image of hue=5, saturation=26,
brightness=60, contrast=62, and white balance=10,000K in the case of an
incandescent lamp.
Such data is based upon actual measurement. Although it may have a slight
difference on the effect of any other environmental factor rather than
illuminance or lighting, it deserves acceptance when considering human
eyesight.
Since lighting of an incandescent lamp is brighter than no light, i.e., a
darkroom, brightness of a picture must be strengthened. Since a red color
component of an incandescent lamp is larger, a red color signal must be
relatively reduced by controlling hue and saturation of a picture. Thus,
there appears different data in each mode.
The representative feature of the embodiment so far discussed is to find
the exterior environment by reading quantized color (R, G, and B) signals
from a color sensor, and thereby to compensate for an original image.
Another embodiment compensating for received image data will be disclosed
with reference to FIGS. 7A and 7B, and FIGS. 8A and 8B.
This embodiment relates to image compensation methods which compensate for
an image data by computing the summation of the electrical value of the
quantized or digitized color signal (R, G, and B), or by judging the
magnitude of R and B and the correlation between them.
The summation (S) of the value of the quantized color signals R, G, and B
(in the case of 6-bits) correlates with illuminance of the exterior
lighting. From the value S, an image compensation data is, as a first
step, determined, and thereby the original image data is compensated for.
Thereafter, as a second step, white balance is compensated for by the
value B-R or R-B as shown in FIG. 7B.
Specifically, FIG. 7A shows image compensation data of a set whose contrast
step ranges from 30 to 100, the brightness step ranges from 40 to 60, the
saturation step ranges from 40 to 55, and the sharpness step ranges from
30 to 60. As first image compensation data, the data are determined
according to the summation of R, G, and B, i.e., the illuminance of
exterior lighting.
FIG 7B shows, as second image compensation data, that if the summation of
the quantized R, G, and B lies within a regular range, the data are
determined by the difference and correlation between R and B.
The second image compensation data additionally compensates for white
balance of a picture and accordingly accomplishes complete color
reproduction according to the exterior lightings.
The system according to this embodiment reads the analog-to-digital
quantized value from the color sensor, and computers R-B or B-R.
Thereafter, it compares the value of R-B or B-R with G of exterior
lighting, and thereby searches for image compensation data for brightness,
saturation, contrast, sharpness, and white balance in a software table.
The found image compensation data compensates for the original image data.
Here, the reason for computing both R-B and B-R is that the software
method is not capable of dealing with a negative computation.
FIGS. 8A and 8B show flowcharts explaining the operation of this
embodiment, based upon the tables indicated in FIGS. 7A and 7B. The
flowcharts indicate how compensation data, according to the values of R,
G, and B from the color sensor, are produced.
From the foregoing, the present invention measure image data, such as hue,
contrast, brightness, saturation, and white balance, changing the
conditions of exterior lightings. And it establishes a data base by the
measured data. The data base is stored in a memory in a microprocessor.
The present invention determines current exterior environment using the
measured data from the data base, and automatically compensates for hue,
saturation, contrast, brightness, and white balance of a picture.
Accordingly, an image is reproduced with complete fidelity, and therefore a
high-quality picture can be produced.
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